1. Field of the Invention
The present invention relates to a special reproduction data generating device for generating special reproduction data from an MPEG transport stream and to a program recording medium a recording medium, a medium, and an information on aggregate.
2. Related Art of the Invention
Special reproduction such as cue and review as well as normal-speed reproduction is performed on AV data, which is based on MPEG transport streams recorded in a medium including a tape medium such as digital VTR.
Such special reproduction is conducted as in the following. Namely, a special reproduction data area is provided on a track locus of a tape medium such as digital VTR, and special reproduction data is recorded in the data area. As for the special reproduction data, when AV data serving as an MPEG transport stream is recorded in the tape medium, some or all pictures of the AV data are extracted and are recorded in the special reproduction data area as transport packets of the MPEG transport stream.
In other words, in order to realize special reproduction using a tape medium, it is necessary to generate special reproduction data from an MPEG transport stream recorded in a tape medium.
Further, special reproduction as well as normal-speed reproduction is carried out on AV data, which is generated based on an MPEG transport stream recorded in a device such as a hard disk permitting random access.
Such special reproduction is performed as follows: namely, upon recording AV data in a magnetic disk medium, special reproduction information is generated which is indicative of recording positions of all or some I pictures used for special reproduction, and the information is recorded in the magnetic disk medium with the AV data. And then, upon special reproduction, only I pictures used for special reproduction are read from the special reproduction information, are converted into an MPEG transport stream, and are outputted.
As described above, in case of recording AV data in a device such as a digital VTR performing sequential access and in case of recording AV data in a device such as a hard disk performing random access, when recording AV data generated based on an MPEG transport stream, it is necessary to generate special reproduction data to perform special reproduction.
Referring to FIGS. 5 and 6, the following will discuss a conventional image processing device for generating special reproduction data from an inputted MPEG transport stream.
FIG. 5 is a block diagram showing the configuration of a conventional image processing device 60.
The image processing device 60 is configured by an input section 61, a picture selecting section 62, a first conversion section 63, a buffer 64, a picture processing section 65, a second conversion section 66, and an output section 67.
The input section 61 is FIFO (First In First Out) for inputting an MPEG transport stream.
The picture selecting section 62 is a means of selecting pictures used for special reproduction.
The first conversion section 63 is a means of removing a header from a transport packet of selected pictures and making a conversion to an ES(elementary stream) or PES(packetized elementary stream).
Special reproduction discontinuously extracts pictures, so that selected pictures have a mismatch on MPEG SYNTAX in a PTS, DTS and so on.
The buffer 64 is a buffer for accumulating a converted ES or PES and is FIFO having a capacity for storing at least several tens of packets.
The picture processing section 65 is a means of performing processing such that a converted ES or PES matches MPEG SYNTAX.
The second conversion section 66 is a means of adding a header to a processed ES or PES and making a conversion to an MPEG transport stream.
The output section 67 is a means of outputting an MPEG transport stream for special reproduction.
The following will discuss the operation of the conventional image processing device 60 configured as above.
FIG. 6 shows the steps of generating special reproduction data in the image processing device 60. In the image processing device 60, an MPEG transport stream is converted to an ES or PES, an ES or PES is generated for special reproduction, the ES or PES is accumulated in a buffer, and the ES or PES is converted to an MPEG transport stream for special reproduction.
Namely, the input section 61 inputs an original MEPG transport stream from which special reproduction data is generated, and conveys transport packets to the picture selecting section 62.
The picture selecting section 62 selects transport packets having data of pictures used for special reproduction. For example, in the case where pictures are displayed at a rate of 30 frames per second in normal reproduction, if the sixfold-speed special reproduction is performed, pictures used for special reproduction are selected every 5 frames. In other words, transport packets are selected which include data of a selected I frame. When a transport packet including an I frame is selected from MPEG2 transport packets, pictures are selected discontinuously, so that the selected transport packets do not match MPEG SYNTAX.
Hence, the first conversion section 63 removes a header from the selected transport packet and makes a conversion to an ES or PES.
The buffer 64 accumulates the converted ES or PES.
The picture processing section 65 performs processing such that the converted ES or PES matches to the SYNTAX of MPEG.
The second conversion section 66 divides the processed ES or PES, adds a header thereto to reconstruct the transport packet, and makes a conversion to an MPEG transport stream.
The output section 67 outputs the MPEG transport stream for special reproduction.
The conventional image processing device 60 generates special reproduction data as described above.
However, in the image processing device 60, which is a conventional device for generating special reproduction data, an MPEG transport stream is temporarily converted to an ES or PES, special reproduction data is generated, and then the ES or PES is converted back to an MPEG transport stream. Therefore, header information removed for converting an MPEG transport stream to an ES or PES is different from header information added for converting an ES or PES to an MPEG transport stream. Thus, information on a transmission line and so on may be lost, which is included in transport packets of the original MPEG transport stream.
Namely, the conventional special reproduction data generating device may lose information on a transmission line. The information is included in an original MPEG transport stream from which special reproduction data is generated.
Moreover, upon processing pictures, picture information included in an MPEG transport stream changes in size. Further, when a transport stream is converted to an ES or PES, matching of data is lost between a conveyed transport packet and an ES or PES included therein. Therefore, the number of transport packets considerably changes before and after processing. The capacity of the buffer needs to be larger to compensate for a difference between input and output.
Namely, a buffer with a large capacity is necessary for generating special reproduction data.
Also, it is difficult to change a transfer rate of an MPEG transport stream in real time, which is outputted as special reproduction data.
Further, some packets are composed of non-video data such as audio and subtitles, and padding and so on are omitted in a conversion to an ES or PES. Hence, latency is not constant from the time an MPEG transport stream is inputted until the time special reproduction data is outputted, and the latency varies according to the content of the packets.